Go find a new job when you're ready to leave, then leave.
Managers aren’t going through the hassle of making a case to raise/promote you only to dump you later. That would make them look pretty bad to their managers.
Problem is, now they know you're thinking of leaving. Since most of the time people do not leave over a few dollars, they assume, most likely correctly, that something else is pushing you to leave and the money is just delaying the inevitable.
When you do that to your manager, it demonstrates to him that he has a business risk which needs mitigating. So he keeps you for now while he tries to get someone else in a position to take over for you should you go through with your original plan to leave.
I've spent decades in the corporate world and I can't recall a single time that a forced raise like this ended up with either side happy, and nearly 100% of the time one year later the employee is gone for one reason or another.
How would the manager or anyone else know that he is leaving?
He is just simply asking for a "raise". He is not going around telling everyone, hey "i am leaving, give me a raise or i am gone". Now that would be plain silly, lol.
As I said, you look around to leverage yourself so that you know how much you are worth in the market. Lot of devs out there, working at companies for over 5+ years tend to underestimate how much they are worth, and they become a bargain for the company. They are simply too shy to ask for just how much they are worth and companies usually don't give raises to employees (besides the annual small pct increase) unless asked upon.
I think you are misreading what we are talking about on this tangent. Forcing a raise by threatening to leave for a more lucrative job is exactly what we are talking about, and I suggested that it is not a great strategy.
It’s 2018. Everyone is always thinking of leaving. This kind of thinking just doesn’t apply anymore.
Ie: "Based off of LinkedIn/GlassDoor/HackerNew/Friends In Industry/Networking events/Recruiters, I feel like my salary could be more competitive with the marketer"
Basically, you're threatening less so of leaving right now, but that you like your current job, but your mental attachment is already weakening because you are worried about a competitive salary (as opposed to not having to worry about it).